Growth Habits: The body of the plant is a darkish green with normally 10 to 14 sharply defined ribs and large woolly areoles somewhat reminiscent of the Astrophytum genus. The areoles contain small sharp spines that are almost completely hidden by the wool. The plant starts off globular but with age can become slightly columnar. Some plants never offset while others do so quite prolifically.
Scientific name: Echinopsis subdenudata
Common name: Generally known as the Sea Urchin Cactus. (This is a good example of the ‘danger’ of using common names for plants and cacti and succulents in particular. Astrophytum asterias is also known by the common name of Sea Urchin Cactus in many parts of the world). Always try and use the scientific name to avoid any confusion.
Synonym: Echinopsis subdenudatus
Etymology: From the Greek echinos (sea urchin or hedgehog) and opsis (like), referring to the plant's resemblance to sea urchins. Subdenudata refers to the lack of noticeable spines.
Origin: Bolivia
Light: Light shade to full sun for half a day.
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Compost: A good general cactus compost is all that is required for this plant to give of its best.
Water: Average water, allowing the plant to dry out almost completely between waterings.
Flower: White, 18cm long, 10cm wide. Night blooming, Flower usually last only one night. And then wilt very quickly.
Fruit: My own plant has not fruited and I have not been able to find any information on the fruit itself. Since compiling this page Rory who lives in Brazil has sent me a photograph of a subdenudata with fruit. The fruit is dark brown and shiny with a roughish surface and tufts of white hair spaced all over the fruit.
Min. temp: The plant is said to be frost tender with a minimum of 50f. 10c. being the safe temperature, although I must admit I keep mine at least 5 degrees lower than this, although it is bone dry.
Cultivation: This species does not present any major difficulties for the average grower other than the fact that because of its bare body it has a tendency to mark, either with sun scorch or water droplets, so forewarned is forearmed as they say. It is best to try to remove the flower stalks as soon as possible (not something I would normally advocate) as they sometimes tend to start to rot if the plant is watered from overhead.
Habitat: This plant grows in the Bolivian department of Tarija, at a relatively low altitude of 2,000 feet.
Comments: This plant is unusual in its ‘apparent’ lack of spines, but in body shape resembles many other cacti. I say apparent lack of spines, the unwary will soon find out that it does in fact have very small spines, which are pretty well hidden by the woolly areoles. In my experience small spines are just as sharp and hurt just as much as the larger ones. However the plant really comes into its own at flowering time and once it has got to flowering size, even at a couple of inches (6-7 cms.) it will flower on a regular basis and provide several blooms at the same time. The flowers as can be seen in the photograph are quite spectacular, although not particularly long lived. The buds must be among the hairiest in the cacti world and are a curiosity in themselves. The plant is said to be an excellent grafting stock, but I have no experience of this myself. Not the most exotic cacti you will ever come across, but one well worthy of a place in collections and an excellent choice for the less experienced grower, particularly as we have already mentioned it flowers at a young age and relatively small size. It will grow quite happily on a sunny windowsill.